1. Field of the Invention
The present invention relates to a game emulator program, and more particularly to a game emulator program for use in a game machine whose display screen resolution is lower than that of the emulated game machine.
2. Description of the Background Art
State-of-the-art hand-held game machines are advanced to the point that they are capable of emulating legacy video game machines, or the like. An emulator program for emulating Nintendo Entertainment System, a legacy video game machine, on Game Boy Advance®, a state-of-the-art hand-held game machine, is currently under development. By running the emulator program on Game Boy Advance®, games for Nintendo Entertainment System can be played on Game Boy Advance®.
There are disclosed, in the prior art, emulation techniques that enable games designed for other game machines to be played on a hand-held device.
However, Nintendo Entertainment System is connected to a television set and produces a game image with a resolution of 240×256 (vertical×horizontal) dots, whereas the liquid crystal monitor of Game Boy Advance® has a lower resolution of 160×240 (vertical×horizontal) dots. Therefore, when a game image of Nintendo Entertainment System is displayed as it is on the liquid crystal monitor of Game Boy Advance®, the upper 40 horizontal lines and the lower 40 horizontal lines (or the lower 80 horizontal lines) of the game image are not displayed, whereby the game becomes unplayable in such non-displayable areas. Thus, in a case where game software designed for a particular game machine is run on another game machine, the difference in display screen resolution causes a problem. No effective solution to this problem has yet been proposed in the art.
One possible solution to the problem is to match the vertical resolution of the game image to that of the liquid crystal monitor of the Game Boy Advance® by evenly decimating the game image by 80 horizontal lines. In such a case, however, the game image is partially dropped for the decimated horizontal lines, thereby detracting from the atmosphere of the original game of Nintendo Entertainment System.
Another possible solution is to employ a general image processing method for resolution adjustment, whereby the number of pixels is reduced by taking an average of pixels around each predetermined pixel in the image. However, such an image process imposes a substantial computational load and is not suitable for use with a game emulator program that runs a game in real time while emulating a heterogeneous game machine.